This is grabbing the hammer by the head, not the handle.
The problem is the total cost of launching a satellite - most of which is the cost of boosting it into orbit. To correct that, you don't need tugboats or shuttles, you need cheap lift systems.
You need to make the cost of putting a bird up low enough that you can plan on a controlled deorbit at end-of-life. Right now, the bird's owner will squeeze every last second of use out of the bird because it is so damn expensive. So they won't plan to save the last N kilos of fuel to deorbit it - that fuel translates into another year of operation.
The problem of boosting a bird into orbit can be split into three parts: initial lift, orbital insertion, and orbital circularization.
For initial lift, you just need a rocket that gets about 90% of the work done. If it gets 85% done, or 95% done, you can correct that in the next phase. As a result you don't need a complicated first stage. What I suggest is a rocket made out of a renewable resource for the casing, coupled with a simple propellant.
That's right, I am suggesting a big Estes rocket. A rocket with a casing made of paper, and solid fuel. A rocket that can set on the shelf for months before use, rather than a liquid fuel rocket that requires constant maintainance before launch. A rocket that is cheap enough to throw away - remember that every kilo you add to the rocket to be able to reuse it is over ten kilos of fuel, or a kilo of payload GONE. I call this the BPR - Big Paper Rocket concept.
For the second part, orbital insertion, you need a rocket that is controllable so you can make up the last 5-15% of the boost. Again, use a cheap system - solid fuel, liquid oxidizer. You throttle the rocket by controlling the oxidizer feed, but the fuel is solid. This has many of the advantages of the BPR - longer shelf life, simpler to make.
The last part, orbital circularization, requires a light motor - it's staying up with the bird, so we need to shave kilos. This is where a high specific impulse system like ion drive or liquid fuel is worth its mass in gold, quite literally.
Make the system cheap enough that you can launch a bird for less than a couple of million dollars, and the owners will not have a problem with deorbiting a bird before it is completely dry.
This way, you avoid having old birds with less than state-of-the-art systems cluttering the sky, taking places that a new craft could do twice the work in. This way, you avoid complex docking manuevers. This way, you bring the cost of getting stuff into space down where it is USEFUL to have a space station. This way you pave the way for Moon and beyond.
OK, that's my opinion. Pick it apart. Or, if you think I'm on to something, start beating on the Planetary Society, the National Space Society, vulture capitalists, NASA, and your congressmutants to make it happen.
True, bogus WHOIS data makes it very hard to track down spamm^H^H^H^H^Htroublemakers on the 'Net, but is this really Verisign's fault?
If I register floobydust.com, and I fill in a contact email that becomes invalid three days after I go live, is that Verisign's fault? What should they do, spam everybody in their WHOIS and purge the bounces?
I can think of lots of reasons to yank Verislime's ability to sell domains, but I'm not sure this is one of them.
Re:Houston wasn't bad, despite amusement park trac
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Lulu Tech Circus
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· Score: 1
KSC isn't bad, but it's not as great as you might think.
I can see an SR-71, a V2, Redstone rockets, Apollo 13 (the real deal), Russian Soyez and Vostok capsules, Chuck Yeager's jacket, Svetlana's space suit.
Damn it, that's twice in one day! First I cannot blast N'Sync out of space, then I hear about somebody not hitting a business major with a cell phone stapled to his head! To borrow a line from an acquaintance of mine, "God I'm so depressed".
How do you tell the difference between a business major hit by a car and a deer hit by a car? Skidmarks in front of the deer.
So, we have a story submitted by an AC, linking to a site with very little information on it. Mayhaps the AC was the site operator?
Now, how does this generate all the frames? Does it require the 802.11 interface to be on the Linux box, or does it manage to send the data to the interface as normal packets. In other words, if I am using one of the Linksys router/802.11 boxes, can I run this on my normal Linux box, or do I need to hack the Linksys to run Linux?
And what is the effect on throughput? Any time the system is sending a fake frame, that is time it cannot be sending real data.
I just want a way to stop the damn Klez worms I keep getting emailed from pixie.udw.ac.za (a university in South Africa). I've mailed their admin repeatedly, mailed their faculty, even mailed their upstream. The closest thing to a response I've gotten was a response from one of the faculty saying "Yeah, we are getting hammered by that too."
What we need is a good way to force admins to actually ADMINISTER the systems they are responsible for, and should they refuse, to get the upstream to null-route the machine until it is fixed.
Considering the trollish way you started this out, why should I be concerned about your links? Let us look at them: HMMM. Most of them seem to be coming from the very company that claims to have a solution. Wouldn't think they'd be biased, now would they?
Secondly, you didn't refute my point about signal mixing in the presence of multiple transmitters - two devices operating at 10GHz can be mixed down into the GPS band by a) their own front ends, b) a corroded fitting in the aircraft, c) the front end of the aircraft's radio, or d) any and all of the above. Having had to RDF signals being created by the mix products of multiple transmitters by old rusty fences, faulty equipment, and other nonlinear sources I know from personal experience that this can happen.
Furthurmore, my point was that the various air control agencies have good reason to be concerned, a point I think I made.
Lastly, the solution to doubling on the radio is not some magical box that will detect it (since it is very difficult to detect another transmitter at any distance from you when you are transmitting on that frequency yourself, it is what pilots and ATC personell are trained to to: acknowledge the transmission! That way, you not only deal with doubles, but misunderstandings too.
I am *discussing* this information because I've encountered far too many people like yourself who don't want to consider any viewpoint other than their own, and I've watch bad law and bad tech result from it. I am trying to be calm and reasonable. I leave it up to the reader to determine whether I have succeeded, and whether you have even tried.
However, if you wish to discontinue the discussion I have no problem with that. You've said what you want to say, and included your links. I've said what I want to say. Let the reader decide.
First of all, "two transmitters on the same frequency" is exactly why aircraft radios still use AM - so that you can hear both signals, unlike FM where capture effect will only let you hear one signal. And to a radio engineer, "heterodyne detection" means "demodulating a signal via mixing of two different frequency signals".
And so what if you can detect a collision - that doesn't help you do diddly about it except try again. And if the interfering carrier is constantly present, you won't get through the second time, either.
The primary concern for aviation interference would be ATCRBS at 1.030 GHz and GPS at 1.5 and 1.7 GHz. That's why I discussed them.
At -41.25 dBm/MHz, you still have over -30 dBm interference in the GPS band, so merely appealing to part 15 won't work there. Additionally, the FCC does not regulate the world - what happens when somebody from Singapore boards an aircraft with a device that isn't following type 15 rules (as has happened in the past.)
Also, if you have multiple UWB devices on the aircraft, they can heterodyne through any corroded fitting, any non-linearity in any receiver to produce mixing products across the board. 2 devices could easily mix down into the 1.03 and 1.5 GHz bands. Get more than a few devices on the plane and you could very easily raise the noise floor on GPS to a level that introduces errors. And when you are on GPS controlled final approach as the aviation industry wants to do, an error of a few meters can spell the difference between "Please remains seated until the aircraft comes to a complete stop" and "Mobilize emergency units to 19L".
The whole point here is that the UWB snakeoil salesmen try to say "We won't interfere - we're MAGIC" and they are full of it. UWB is just another transmitter, and the aviation regulators are quite correct in being concerned about this.
I am working with the people DOING these tests - are you?
May I ask what you think you mean by "heterodyne detection"? Because all the aviation band radios I've ever designed test equipment for were superheterodyne receivers, just like any other modern radio.
The problem with UWB is that simple fact that it occupies the same spectrum as everything else, by design - as a result it acts to raise the noise floor of all signals.
This isn't a problem when you are dealing with a signal that is tens of decibels above the noise floor, but if you are dealing with a weak signal, like GPS, LORAN, or another aircraft's ATCRBS transponder where you only have a few dB headroom, you don't have any leeway for the noise floor to rise. It doesn't matter what supercalofragilistic sheilding you put on anything to keep unwanted frequencies out, because UWB occupies the wanted frequencies too!.
And as for the tech in aviation not changing - tell it to the trial lawyers who pounce on any excuse to sue aviation manufacturers. If anybody introduces something new, and the plane it is in crashes, then the manufacturer will be sued for putting in "New, Experimental, untested technology!" - even if the reason the plane crashed was that the pilot was drunk, stoned, and inexperenced. So neither the manufactures nor the FAA will approve any new tech without giving it a multi-decade probe.
Let me run the numbers for you on interference.
Assume you have a UWB device at 10 mW output. Assume the bandwidth is 3 GHz, centered at 2 GHz. Assume the spectral shaping is rectangular. Thus, the energy is evenly spread from.5 GHz to 3.5 GHz.
First observation: the signal overlaps the GPS frequency allocation.
OK, now what is the power density? 10 mW over 3 GHz is 3.3E-12 W/Hz.
Now, consider GPS. GPS signals are about 20.46MHz wide. That means our UWB signal will be producing 3.3E-12 W/Hz * 20.46 MHz = 6.8E-5 Watts of signal, or -11.6 dBm of signal. The signal you get from the birds is less than about -90 dBm. You UWB signal is over 80 dB HIGHER than the GPS signal. Even with the coding gain you get from the fact that GPS is spread-spectrum you are still 30 dB under the noise floor. That means you could reduce the UWB signal by 30 dB (1/1000 the power) and STILL swamp the GPS signal.
UWB isn't magic - it doesn't magically pull bandwidth from nowhere, and it WILL interfer with other signals. You want to park the signal in a band nobody else is using, like up in the THz band, great! But don't put it down with everybody else, because contrary to what its proponents say, it does not play well with others.
I didn't mean to imply you won't get generation of H2 and O2 at the electrodes - of course you will.
However, many posters assert that you will get metallic sodium and pure chlorine in the mix, and that is wrong.
As any chemist will tell you, when you mix NaCl into H20, you will have Na+ and Cl- ions in the water - no electricity needed. However, remove the water and the NaCl will reform.
What the electrolysis reaction does is break the H2O into H+ and OH- ions. Some of the H+ ions will combine into H2 at at the negative electrode, and some of tho OH- ions will combine into O2 and H2O at the plus electrode, releasing the commonly observed gases.
However, some of the H+ ions will also combine with the CL- ions to yeild HCL, which will furthur react to produce hypochlorus acid (which, if you had studied anything more than basic chemistry, you would recognise as bleach).
Additionally, some of the OH- ions will react with the Na+ ions to form NaOH.
Now, this is NOT an equilibrium state - in the absense of the electric current the hypochlorous acid will recombine with the sodium hydroxide to reform water and salt. Hence why you have to seperate the solutions at the electrodes - yeilding a mild bleach solution and a mild lye solution.
Rather, you get a hypochlorous acid ion, an a sodium hydroxide ion. In effect, the reverse of mixing hypochlorous acid and lye.
However, you get it in VERY dilute quantities, nowhere near what you'd need to damage human skin. But if you are an itty bitty microbe, the oxidizing effect is deadly.
Really, this is just a "bleach on demand" sort of thing.
So find yourself a shop that rebuilds battery packs. Everybattery.com has franchise stores in several big (and not so big) cities, and those franchises will rebuild damn near any battery pack you bring in.
Also, go to a library and look in a QST magazine - there will be scadloads of places that will rebuild battery packs for you.
The only question is, "Is it worth it to have this pack rebuilt, or should I just buy a new whatever?"
You don't give us any idea of what your current skill set is, so it is hard to offer meaningful advice.
Question: is your skill set rare enough that your current employer might be conviced to allow you to work remotely most of the time? Perhaps you can offer to telecommute 3 out of 4 weeks, and be on site for the 4th week. True, if there are more people with your skill set than there are jobs you are screwed, but the fact that you are currently employed suggests that may not be the case.
You may also be able to start consulting in your current work area, and thus travel to the customers' sites. You might be away from your wife for much of the time, but if you are bringing in enough money you can consult 9 months out of the year, and coast the other 3. That may even work out better depending upon your wife's schedule - you may find you can take a nice vacation over the summer months.
Otherwise, you will have problems - if a job can be outsourced to Joe Bloggs in the USA over the phone, it can be outsourced to Miguel Jloggs in Mexico, Chackra Coggs in India, etc. If your skill set isn't rare enough, you can be replaced, so you will have problems.
Can you give us a hint as to what area you are in?
I'm not sure I'd trust Ximian to auto-update my system - while they try pretty hard, I've had just too many dependancy conflicts updating RPMS from them to feel really warm and fuzzy about having it happen automatically.
Also, one thing I like about RedHat's up2date vs. RedCarpet is that I can tell up2date to leave my damn X server alone!. Neither RedHat 7.2 nor Ximian have XFree 4.2, but at least I can tell up2date "hands off any package with XFree in the title" and not worry about it downgrading me to 4.1. Every time I run RedCarpet I have to tell it "No, I DON'T want you updating my X server, yes I know this is a "security release", but I don't need it!"
Unless redcarpetd has the ability to prevent upgrades on selected packages I wouldn't trust it.
And until the packages get vetted better for conflicts I would be careful. That's what ALL RPM based distro's need - a standard base of packages and libraries that released packages are not allowed to deviate from. Any RPM that call for "foo-1.4.2-unreleased-unstable-pl1.4-thursday.rpm" should be uncerimoniously bounced from any stable release. That's one area I will give the Debian folks credit - they maintain their packages.
And how many throw away their Second...
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Want Freedom?
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· Score: 3, Insightful
I find it surprising and depressing that many who will complain bitterly about any infringement upon their or anybody else's First amendment rights will support trampling on the rights granted under the Second Amendment (our own beloved Cmdr. Taco being a prime example).
Free Speech is just as dangerous as a gun - anybody who has seen a riot (or a lynch mob) being incited will attest to that.
The Founding Fathers held the right to free expression and the right to self defense as inalienable rights (as in, you cannot be forced to surrender those rights under any circumstances). This was because they knew that without the ability to defend them, by force if necessary, we would lose them.
And look at what is happening. Little by little we are deprived of our freedom of expression, and denied any peaceful means to oppose this.
I don't want to see violence be the only alternative. I don't want to see violence be used. But if we lose the option, and then we lose all other alternatives....
SO, when you register the game, make sure you register with the registration card, not online.
Then, VERY VISIBLY, where they ask you what version of Windows you are running, SCRATCH THEM ALL OUT and write in "Wine Under Linux".
That way, the companies get some feedback that, dispite their best efforts to deny it, there actually IS a market segment out there that
Will pay for games
Runs them under Linux (or BSD or whatever...)
Will go to GREAT LENGTHS to do so.
That's why I registered my new Sony DV camcorder - because I could write in that I was using it with a Linux machine (thanks to Kino). That's why I am going to register my new Casio BZX201 watch - the software to update the contact data runs very nicely under Wine (although I may try to get a programming guide out of them and make a proper applet for it.)
Just DON'T register with the game's online registration program - it will ask Wine what version of Windows it is, and Wine will (needfully) lie and say it is whatever version of Windows you have it faking, and the company will NOT get the feedback you want them to get.
(OT: don't let your browswer lie and say it is IE when it isn't - if the damn web page won't work with Moz|Galeon|Konq|..., screw them. I wonder how many of the 96% of the browsers that claim to be IE are really not...)
I have Halflife and Halflife-Opposing Force running quite nicely under vanilla Wine, and running as well as native. Perhaps I might be able to give you some pointers? What problems are you having?
I find it very strange that a Slashback would criticize a news web site for silently altering a story, when Slashdot itself does this on a regular basis.
Come on guys, show the world the correct way - make ALL the editors make ALL changes as addenda to the story, rather than in-line. After all, if I cannot change my posting once I hit SUBMIT, then you shouldn't be able to change your stories.
If you wish to correct minor speling (sic) errors, then correct them by marking the old text as strikethrough, and then inserting the new. Yes, it won't look as nice, but it will be more honest. And perhaps when the/. editors see how many strikethroughs the main page has, they will incorporate a spell check into the story submission system.
The good Doctor (Asimov) wrote a story about this very effect: "When the Saints".
In the story, a musician is hired by a psychologist to assist in a research project. They are recording the brainwaves of depressed patients, diffing them against the brain waves of normal folks, inverting the difference, and feeding that back into the patient with sound and laserlight. It works, sort of, for a while.
They hire the musician because (rough quote) "...while the laser light is precise enough to convey the information, the sound isn't. We need somebody to work out what part of the sound is important, and what part isn't."
The musician takes the tapes and goes away for a while. When he returns, he says, "Here's a tape. Try this." The psychologist cues the tape up for the patient. After the session, the patient says "I think I'm cured - before I always could feel the depression in the back of my mind, but it's gone now!" "Did you notice anything different about the therapy?" "Well, maybe the light was a bit sharper..." "What about the sound?" "I really didn't notice the sound..."
After the patient leaves, the psychologist asks the musician what he did, and would he consider a position on the staff.
(Roughly quoting the musician) "No need - the work's already been done. I noticed the patterns were like some music I know - revival hymns. I gave him the best of the lot - When The Saints Go Marching In"
Dr. Asimov wrote this for an Audio magazine, and the story appears in some of his story collections. Good stuff.
If you are ever in Idaho, you should visit EBR-1, the world's first breeder reactor. It is decommissioned, cold, and open for tourists during the summer season. Outside, they have some prototype nuclear jet engines - devices that took in air, heated it with a fission reactor, and expelled it for thrust. Neat stuff - would have been nasty as hell had it ever gone into service, but neat none the less.
Caffeine overdose isn't much fun. While it is a lot harder to reach LD50 (Lethal Dose 50% - the amount of a substance required to kill half those who take that amount) on caffeine verses alchohol, it is possible. And even if you don't get sick, you can still get sick.
Back when I was an undergrad, I had a Statics final on Saturday (in a large engineering school, you have enough students taking Statics (not Statistics - Statics : the study of forces on non-moving systems) that it's easier for them to have it on a Saturday in a BIG auditorium). I'd played AD&D to three o'clock in the morning, and the final was at 7 o'clock. Factor in transit time back to my dorm room and you get something less than three hours of sleep.
So, I fixed a big pot of coffee in the morning, and took 2 NoDoze tablets, and went to the final. I figured "No problem - I'll get breakfast and slow down the absorption of the caffeine, and all will be well." Except the dorm cafeteria didn't open until 9:30 on weekends. Ooops!.
I finished the final, but my hands were vibrating in the shortwave band, my stomach was running about 150 RPM, and the less said about my lower GI tract the better. It took the better part of the day to recover.
Caffeine is an antagonist - it blocks the effect of a neurotransmitter. So, unlike active drugs like cocaine or speed, past a certain point you will get no more effect from caffeine - you've blocked all the neurotranmitters you are going to block. Past that point you are simply getting all the side effects of caffeine. Furthurmore, blocking the neurotranmitter only provides a temporary boost to wakefulness - after a while you no longer have any of the OTHER neurotransmitters you need to function, and you will fall over.
I'd second the good advice given by others in this forum - if you are tired, SLEEP! At the least, take a catnap and come back to it.
Especially for something like a LAN game - it's not life or death, so why screw yourself up? It's supposed to be FUN!
The CDPD system involves sending short, relatively low speed data bursts over a voice channel of standard North American Analog Phone Service (AMPS). This allows a standard AMPS system to carry CDPD with little retrofitting of the cell towers, whereas GPRS requires a whole new system. Given that your average cell site runs about US$1M, that adds up very quickly.
CDPD is a CS/A TDMA system (Collision Sense/Collision Avoidance Time Domain Multiple Access) system - Multiple users transmit on the same frequency at different times, much like Ethernet.
CDPD is in common use for vending machines, electric meters, and other systems that need to report relatively little information.
When it first came out, years ago, I thought "YOU IDIOTS! You are pricing this PER PACKET - it will never sell. Price it flat rate and people will eat it up!" Guess what - now they are starting to look at pricing it flat rate, and it is now becoming attractive!
CDPD operates in the 800MHz US Cellular band. It can use encryption based on RSA.
Slashdot Mirror
This is grabbing the hammer by the head, not the handle.
The problem is the total cost of launching a satellite - most of which is the cost of boosting it into orbit. To correct that, you don't need tugboats or shuttles, you need cheap lift systems.
You need to make the cost of putting a bird up low enough that you can plan on a controlled deorbit at end-of-life. Right now, the bird's owner will squeeze every last second of use out of the bird because it is so damn expensive. So they won't plan to save the last N kilos of fuel to deorbit it - that fuel translates into another year of operation.
The problem of boosting a bird into orbit can be split into three parts: initial lift, orbital insertion, and orbital circularization.
For initial lift, you just need a rocket that gets about 90% of the work done. If it gets 85% done, or 95% done, you can correct that in the next phase. As a result you don't need a complicated first stage. What I suggest is a rocket made out of a renewable resource for the casing, coupled with a simple propellant.
That's right, I am suggesting a big Estes rocket. A rocket with a casing made of paper, and solid fuel. A rocket that can set on the shelf for months before use, rather than a liquid fuel rocket that requires constant maintainance before launch. A rocket that is cheap enough to throw away - remember that every kilo you add to the rocket to be able to reuse it is over ten kilos of fuel, or a kilo of payload GONE. I call this the BPR - Big Paper Rocket concept.
For the second part, orbital insertion, you need a rocket that is controllable so you can make up the last 5-15% of the boost. Again, use a cheap system - solid fuel, liquid oxidizer. You throttle the rocket by controlling the oxidizer feed, but the fuel is solid. This has many of the advantages of the BPR - longer shelf life, simpler to make.
The last part, orbital circularization, requires a light motor - it's staying up with the bird, so we need to shave kilos. This is where a high specific impulse system like ion drive or liquid fuel is worth its mass in gold, quite literally.
Make the system cheap enough that you can launch a bird for less than a couple of million dollars, and the owners will not have a problem with deorbiting a bird before it is completely dry.
This way, you avoid having old birds with less than state-of-the-art systems cluttering the sky, taking places that a new craft could do twice the work in. This way, you avoid complex docking manuevers. This way, you bring the cost of getting stuff into space down where it is USEFUL to have a space station. This way you pave the way for Moon and beyond.
OK, that's my opinion. Pick it apart. Or, if you think I'm on to something, start beating on the Planetary Society, the National Space Society, vulture capitalists, NASA, and your congressmutants to make it happen.
True, bogus WHOIS data makes it very hard to track down spamm^H^H^H^H^Htroublemakers on the 'Net, but is this really Verisign's fault?
If I register floobydust.com, and I fill in a contact email that becomes invalid three days after I go live, is that Verisign's fault? What should they do, spam everybody in their WHOIS and purge the bounces?
I can think of lots of reasons to yank Verislime's ability to sell domains, but I'm not sure this is one of them.
KSC isn't bad, but it's not as great as you might think.
But again, I'm spoiled.
I can see an SR-71, a V2, Redstone rockets, Apollo 13 (the real deal), Russian Soyez and Vostok capsules, Chuck Yeager's jacket, Svetlana's space suit.
Then I can go eat homemade Amish pie.
I would rather know the pitch of viscosity - is it middle-C, or something else?
Damn it, that's twice in one day! First I cannot blast N'Sync out of space, then I hear about somebody not hitting a business major with a cell phone stapled to his head! To borrow a line from an acquaintance of mine, "God I'm so depressed".
How do you tell the difference between a business major hit by a car and a deer hit by a car? Skidmarks in front of the deer.
(which was the title of my submission - I think mine is better....)
But damn it, I wanted him in space. Oh well, plans change.
Anybody want to buy a ground-to-space interceptor rocket?
So, we have a story submitted by an AC, linking to a site with very little information on it. Mayhaps the AC was the site operator?
Now, how does this generate all the frames? Does it require the 802.11 interface to be on the Linux box, or does it manage to send the data to the interface as normal packets. In other words, if I am using one of the Linksys router/802.11 boxes, can I run this on my normal Linux box, or do I need to hack the Linksys to run Linux?
And what is the effect on throughput? Any time the system is sending a fake frame, that is time it cannot be sending real data.
I just want a way to stop the damn Klez worms I keep getting emailed from pixie.udw.ac.za (a university in South Africa). I've mailed their admin repeatedly, mailed their faculty, even mailed their upstream. The closest thing to a response I've gotten was a response from one of the faculty saying "Yeah, we are getting hammered by that too."
What we need is a good way to force admins to actually ADMINISTER the systems they are responsible for, and should they refuse, to get the upstream to null-route the machine until it is fixed.
Considering the trollish way you started this out, why should I be concerned about your links? Let us look at them: HMMM. Most of them seem to be coming from the very company that claims to have a solution. Wouldn't think they'd be biased, now would they?
Secondly, you didn't refute my point about signal mixing in the presence of multiple transmitters - two devices operating at 10GHz can be mixed down into the GPS band by a) their own front ends, b) a corroded fitting in the aircraft, c) the front end of the aircraft's radio, or d) any and all of the above. Having had to RDF signals being created by the mix products of multiple transmitters by old rusty fences, faulty equipment, and other nonlinear sources I know from personal experience that this can happen.
Furthurmore, my point was that the various air control agencies have good reason to be concerned, a point I think I made.
Lastly, the solution to doubling on the radio is not some magical box that will detect it (since it is very difficult to detect another transmitter at any distance from you when you are transmitting on that frequency yourself, it is what pilots and ATC personell are trained to to: acknowledge the transmission! That way, you not only deal with doubles, but misunderstandings too.
I am *discussing* this information because I've encountered far too many people like yourself who don't want to consider any viewpoint other than their own, and I've watch bad law and bad tech result from it. I am trying to be calm and reasonable. I leave it up to the reader to determine whether I have succeeded, and whether you have even tried.
However, if you wish to discontinue the discussion I have no problem with that. You've said what you want to say, and included your links. I've said what I want to say. Let the reader decide.
First of all, "two transmitters on the same frequency" is exactly why aircraft radios still use AM - so that you can hear both signals, unlike FM where capture effect will only let you hear one signal. And to a radio engineer, "heterodyne detection" means "demodulating a signal via mixing of two different frequency signals".
And so what if you can detect a collision - that doesn't help you do diddly about it except try again. And if the interfering carrier is constantly present, you won't get through the second time, either.
The primary concern for aviation interference would be ATCRBS at 1.030 GHz and GPS at 1.5 and 1.7 GHz. That's why I discussed them.
At -41.25 dBm/MHz, you still have over -30 dBm interference in the GPS band, so merely appealing to part 15 won't work there. Additionally, the FCC does not regulate the world - what happens when somebody from Singapore boards an aircraft with a device that isn't following type 15 rules (as has happened in the past.)
Also, if you have multiple UWB devices on the aircraft, they can heterodyne through any corroded fitting, any non-linearity in any receiver to produce mixing products across the board. 2 devices could easily mix down into the 1.03 and 1.5 GHz bands. Get more than a few devices on the plane and you could very easily raise the noise floor on GPS to a level that introduces errors. And when you are on GPS controlled final approach as the aviation industry wants to do, an error of a few meters can spell the difference between "Please remains seated until the aircraft comes to a complete stop" and "Mobilize emergency units to 19L".
The whole point here is that the UWB snakeoil salesmen try to say "We won't interfere - we're MAGIC" and they are full of it. UWB is just another transmitter, and the aviation regulators are quite correct in being concerned about this.
I am working with the people DOING these tests - are you?
May I ask what you think you mean by "heterodyne detection"? Because all the aviation band radios I've ever designed test equipment for were superheterodyne receivers, just like any other modern radio.
.5 GHz to 3.5 GHz.
The problem with UWB is that simple fact that it occupies the same spectrum as everything else, by design - as a result it acts to raise the noise floor of all signals.
This isn't a problem when you are dealing with a signal that is tens of decibels above the noise floor, but if you are dealing with a weak signal, like GPS, LORAN, or another aircraft's ATCRBS transponder where you only have a few dB headroom, you don't have any leeway for the noise floor to rise. It doesn't matter what supercalofragilistic sheilding you put on anything to keep unwanted frequencies out, because UWB occupies the wanted frequencies too!.
And as for the tech in aviation not changing - tell it to the trial lawyers who pounce on any excuse to sue aviation manufacturers. If anybody introduces something new, and the plane it is in crashes, then the manufacturer will be sued for putting in "New, Experimental, untested technology!" - even if the reason the plane crashed was that the pilot was drunk, stoned, and inexperenced. So neither the manufactures nor the FAA will approve any new tech without giving it a multi-decade probe.
Let me run the numbers for you on interference.
Assume you have a UWB device at 10 mW output. Assume the bandwidth is 3 GHz, centered at 2 GHz. Assume the spectral shaping is rectangular. Thus, the energy is evenly spread from
First observation: the signal overlaps the GPS frequency allocation.
OK, now what is the power density? 10 mW over 3 GHz is 3.3E-12 W/Hz.
Now, consider GPS. GPS signals are about 20.46MHz wide. That means our UWB signal will be producing 3.3E-12 W/Hz * 20.46 MHz = 6.8E-5 Watts of signal, or -11.6 dBm of signal. The signal you get from the birds is less than about -90 dBm. You UWB signal is over 80 dB HIGHER than the GPS signal. Even with the coding gain you get from the fact that GPS is spread-spectrum you are still 30 dB under the noise floor. That means you could reduce the UWB signal by 30 dB (1/1000 the power) and STILL swamp the GPS signal.
UWB isn't magic - it doesn't magically pull bandwidth from nowhere, and it WILL interfer with other signals. You want to park the signal in a band nobody else is using, like up in the THz band, great! But don't put it down with everybody else, because contrary to what its proponents say, it does not play well with others.
I didn't mean to imply you won't get generation of H2 and O2 at the electrodes - of course you will.
However, many posters assert that you will get metallic sodium and pure chlorine in the mix, and that is wrong.
As any chemist will tell you, when you mix NaCl into H20, you will have Na+ and Cl- ions in the water - no electricity needed. However, remove the water and the NaCl will reform.
What the electrolysis reaction does is break the H2O into H+ and OH- ions. Some of the H+ ions will combine into H2 at at the negative electrode, and some of tho OH- ions will combine into O2 and H2O at the plus electrode, releasing the commonly observed gases.
However, some of the H+ ions will also combine with the CL- ions to yeild HCL, which will furthur react to produce hypochlorus acid (which, if you had studied anything more than basic chemistry, you would recognise as bleach).
Additionally, some of the OH- ions will react with the Na+ ions to form NaOH.
Now, this is NOT an equilibrium state - in the absense of the electric current the hypochlorous acid will recombine with the sodium hydroxide to reform water and salt. Hence why you have to seperate the solutions at the electrodes - yeilding a mild bleach solution and a mild lye solution.
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The reaction isn't, as some have said:
NaCl + 2H20 + electricity -> Na + Cl + 2H2 + O2
Rather, you get a hypochlorous acid ion, an a sodium hydroxide ion. In effect, the reverse of mixing hypochlorous acid and lye.
However, you get it in VERY dilute quantities, nowhere near what you'd need to damage human skin. But if you are an itty bitty microbe, the oxidizing effect is deadly.
Really, this is just a "bleach on demand" sort of thing.
So find yourself a shop that rebuilds battery packs. Everybattery.com has franchise stores in several big (and not so big) cities, and those franchises will rebuild damn near any battery pack you bring in.
Also, go to a library and look in a QST magazine - there will be scadloads of places that will rebuild battery packs for you.
The only question is, "Is it worth it to have this pack rebuilt, or should I just buy a new whatever?"
You don't give us any idea of what your current skill set is, so it is hard to offer meaningful advice.
Question: is your skill set rare enough that your current employer might be conviced to allow you to work remotely most of the time? Perhaps you can offer to telecommute 3 out of 4 weeks, and be on site for the 4th week. True, if there are more people with your skill set than there are jobs you are screwed, but the fact that you are currently employed suggests that may not be the case.
You may also be able to start consulting in your current work area, and thus travel to the customers' sites. You might be away from your wife for much of the time, but if you are bringing in enough money you can consult 9 months out of the year, and coast the other 3. That may even work out better depending upon your wife's schedule - you may find you can take a nice vacation over the summer months.
Otherwise, you will have problems - if a job can be outsourced to Joe Bloggs in the USA over the phone, it can be outsourced to Miguel Jloggs in Mexico, Chackra Coggs in India, etc. If your skill set isn't rare enough, you can be replaced, so you will have problems.
Can you give us a hint as to what area you are in?
I'm not sure I'd trust Ximian to auto-update my system - while they try pretty hard, I've had just too many dependancy conflicts updating RPMS from them to feel really warm and fuzzy about having it happen automatically.
" should be uncerimoniously bounced from any stable release. That's one area I will give the Debian folks credit - they maintain their packages.
Also, one thing I like about RedHat's up2date vs. RedCarpet is that I can tell up2date to leave my damn X server alone!. Neither RedHat 7.2 nor Ximian have XFree 4.2, but at least I can tell up2date "hands off any package with XFree in the title" and not worry about it downgrading me to 4.1. Every time I run RedCarpet I have to tell it "No, I DON'T want you updating my X server, yes I know this is a "security release", but I don't need it!"
Unless redcarpetd has the ability to prevent upgrades on selected packages I wouldn't trust it.
And until the packages get vetted better for conflicts I would be careful. That's what ALL RPM based distro's need - a standard base of packages and libraries that released packages are not allowed to deviate from. Any RPM that call for "foo-1.4.2-unreleased-unstable-pl1.4-thursday.rpm
I find it surprising and depressing that many who will complain bitterly about any infringement upon their or anybody else's First amendment rights will support trampling on the rights granted under the Second Amendment (our own beloved Cmdr. Taco being a prime example).
Free Speech is just as dangerous as a gun - anybody who has seen a riot (or a lynch mob) being incited will attest to that.
The Founding Fathers held the right to free expression and the right to self defense as inalienable rights (as in, you cannot be forced to surrender those rights under any circumstances). This was because they knew that without the ability to defend them, by force if necessary, we would lose them.
And look at what is happening. Little by little we are deprived of our freedom of expression, and denied any peaceful means to oppose this.
I don't want to see violence be the only alternative. I don't want to see violence be used. But if we lose the option, and then we lose all other alternatives....
Then, VERY VISIBLY, where they ask you what version of Windows you are running, SCRATCH THEM ALL OUT and write in "Wine Under Linux".
That way, the companies get some feedback that, dispite their best efforts to deny it, there actually IS a market segment out there that
That's why I registered my new Sony DV camcorder - because I could write in that I was using it with a Linux machine (thanks to Kino). That's why I am going to register my new Casio BZX201 watch - the software to update the contact data runs very nicely under Wine (although I may try to get a programming guide out of them and make a proper applet for it.)
Just DON'T register with the game's online registration program - it will ask Wine what version of Windows it is, and Wine will (needfully) lie and say it is whatever version of Windows you have it faking, and the company will NOT get the feedback you want them to get.
(OT: don't let your browswer lie and say it is IE when it isn't - if the damn web page won't work with Moz|Galeon|Konq|..., screw them. I wonder how many of the 96% of the browsers that claim to be IE are really not...)
Spammers love this - it makes listwashing so much easier...
I have Halflife and Halflife-Opposing Force running quite nicely under vanilla Wine, and running as well as native. Perhaps I might be able to give you some pointers? What problems are you having?
I find it very strange that a Slashback would criticize a news web site for silently altering a story, when Slashdot itself does this on a regular basis.
/. editors see how many strikethroughs the main page has, they will incorporate a spell check into the story submission system.
Come on guys, show the world the correct way - make ALL the editors make ALL changes as addenda to the story, rather than in-line. After all, if I cannot change my posting once I hit SUBMIT, then you shouldn't be able to change your stories.
If you wish to correct minor speling (sic) errors, then correct them by marking the old text as strikethrough, and then inserting the new. Yes, it won't look as nice, but it will be more honest. And perhaps when the
The good Doctor (Asimov) wrote a story about this very effect: "When the Saints".
In the story, a musician is hired by a psychologist to assist in a research project. They are recording the brainwaves of depressed patients, diffing them against the brain waves of normal folks, inverting the difference, and feeding that back into the patient with sound and laserlight. It works, sort of, for a while.
They hire the musician because (rough quote) "...while the laser light is precise enough to convey the information, the sound isn't. We need somebody to work out what part of the sound is important, and what part isn't."
The musician takes the tapes and goes away for a while. When he returns, he says, "Here's a tape. Try this." The psychologist cues the tape up for the patient. After the session, the patient says "I think I'm cured - before I always could feel the depression in the back of my mind, but it's gone now!" "Did you notice anything different about the therapy?" "Well, maybe the light was a bit sharper..." "What about the sound?" "I really didn't notice the sound..."
After the patient leaves, the psychologist asks the musician what he did, and would he consider a position on the staff.
(Roughly quoting the musician)
"No need - the work's already been done. I noticed the patterns were like some music I know - revival hymns. I gave him the best of the lot - When The Saints Go Marching In"
Dr. Asimov wrote this for an Audio magazine, and the story appears in some of his story collections. Good stuff.
If you are ever in Idaho, you should visit EBR-1, the world's first breeder reactor. It is decommissioned, cold, and open for tourists during the summer season. Outside, they have some prototype nuclear jet engines - devices that took in air, heated it with a fission reactor, and expelled it for thrust. Neat stuff - would have been nasty as hell had it ever gone into service, but neat none the less.
EBR-1 is about 4 hours drive from the west entrance of Yellowstone National Park, and about 45 minute from Craters of the Moon National Park, so there's plenty of other stuff to do in the area.
Caffeine overdose isn't much fun. While it is a lot harder to reach LD50 (Lethal Dose 50% - the amount of a substance required to kill half those who take that amount) on caffeine verses alchohol, it is possible. And even if you don't get sick, you can still get sick.
Back when I was an undergrad, I had a Statics final on Saturday (in a large engineering school, you have enough students taking Statics (not Statistics - Statics : the study of forces on non-moving systems) that it's easier for them to have it on a Saturday in a BIG auditorium). I'd played AD&D to three o'clock in the morning, and the final was at 7 o'clock. Factor in transit time back to my dorm room and you get something less than three hours of sleep.
So, I fixed a big pot of coffee in the morning, and took 2 NoDoze tablets, and went to the final. I figured "No problem - I'll get breakfast and slow down the absorption of the caffeine, and all will be well." Except the dorm cafeteria didn't open until 9:30 on weekends. Ooops!.
I finished the final, but my hands were vibrating in the shortwave band, my stomach was running about 150 RPM, and the less said about my lower GI tract the better. It took the better part of the day to recover.
Caffeine is an antagonist - it blocks the effect of a neurotransmitter. So, unlike active drugs like cocaine or speed, past a certain point you will get no more effect from caffeine - you've blocked all the neurotranmitters you are going to block. Past that point you are simply getting all the side effects of caffeine. Furthurmore, blocking the neurotranmitter only provides a temporary boost to wakefulness - after a while you no longer have any of the OTHER neurotransmitters you need to function, and you will fall over.
I'd second the good advice given by others in this forum - if you are tired, SLEEP! At the least, take a catnap and come back to it.
Especially for something like a LAN game - it's not life or death, so why screw yourself up? It's supposed to be FUN!
CDPD - Cellular Digital Packet Data.
The CDPD system involves sending short, relatively low speed data bursts over a voice channel of standard North American Analog Phone Service (AMPS). This allows a standard AMPS system to carry CDPD with little retrofitting of the cell towers, whereas GPRS requires a whole new system. Given that your average cell site runs about US$1M, that adds up very quickly.
CDPD is a CS/A TDMA system (Collision Sense/Collision Avoidance Time Domain Multiple Access) system - Multiple users transmit on the same frequency at different times, much like Ethernet.
CDPD is in common use for vending machines, electric meters, and other systems that need to report relatively little information.
When it first came out, years ago, I thought "YOU IDIOTS! You are pricing this PER PACKET - it will never sell. Price it flat rate and people will eat it up!" Guess what - now they are starting to look at pricing it flat rate, and it is now becoming attractive!
CDPD operates in the 800MHz US Cellular band. It can use encryption based on RSA.
I had done some work on a CDPD tester in the past.